The present invention relates to a reinforced hose, and more particularly to an improvement in an intermediate reinforcing layer in a reinforced hose.
FIG. 4 shows an example of a conventional reinforced hose 1 to be used as a hose for power steering. The reinforced hose 1 is constituted by an inner pipe layer 3 and an outer pipe layer 7, both of which are made of synthetic rubber having a polar group, and an intermediate reinforcing layer 5. Nitrile rubber (hereinafter referred to as "NBR") is employed as the synthetic rubber having a polar group for forming the inner pipe layer 3, and chloroprene rubber (hereinafter referred to as "CR") is employed as that for forming the outer pipe layer 7. The intermediate reinforcing layer 5 is formed by doubly braiding reinforcing fibers which are composed of polyamide and coated with CR.
The reinforcing fibers are coated with CR in order to prevent the reinforcing fibers from being shifted from one another and in order to improve the adhesiveness of the intermediate reinforcing layer to the inner and outer pipe layers 3 and 7 by use of the polarity of CR, and so on. Particularly, CR is more frequently used as a coating material because high adhesiveness is obtained between the outer pipe layer 7 made of CR and the intermediate reinforcing layer 5.
The reinforced hose 1 having such a configuration as described above has sufficient endurance for present purposes.
However, reinforced hoses are now required to be improved in endurance as one of the car parts for which the current trend is towards being maintenance free.